This is an application to fund a new Stage III community-based randomized clinical efficacy trial testing Mothering from the Inside Out (MIO), the first evidence-based parenting intervention designed to be delivered by addiction counselors in addiction treatment settings where parents of young children are enrolled in treatment. In two (Stage I and II) randomized clinical efficacy trials conducted during the first 9 years of this award, when compared with a standard parent education program (PE), MIO demonstrated efficacy for improving parenting, child attachment security and for positively impacting abstinence from drug use. Importantly, mothers with high addiction severity assigned to MIO showed notable improvement across all outcomes. MIO is a weekly individual parenting therapy developed as an enhancement to standard addiction treatment that targets the addicted mother's capacity to recognize and regulate her own emotional distress during stressful parenting situations so that she can support her child's developing capacity for emotional and behavioral regulation. This capacity, called reflective functioning (RF), is a psychological skill that promotes abstinence and also helps parents foster their young children's secure attachment. Now that MIO has demonstrated efficacy in two randomized efficacy trials, the next step will be to conduct a new Stage III community-based efficacy trial where addiction counselors are trained to deliver MIO and PE with fidelity in an addiction treatment setting and to evaluate treatment outcomes and mechanisms of change in this community setting. This will be one of the first investigations implementing a new stage model for intervention research (Onken et al., 2014) where efficacious interventions are first tested under conditions of high internal validity (with treatment fidelity assured) before effectiveness is tested under conditions of high external validity. At the end of this trial, if MIO demonstrates efficacy, we will have allthe necessary materials to train addiction counselors across a broad range of treatment settings in a Stage IV effectiveness trial. In the first year, we will conduct a training pilot where 14 addicton counselors in an addiction treatment clinic will be randomly assigned to training in MIO vs PE delivery and complete a training case with a real patient during which fidelity will be measured. In years 2 - 5, 160 mothers in addiction treatment and caring for children ages 12 - 24 months will be randomized to 12 sessions of MIO vs PE with a trained addiction counselor and fidelity will be monitored and maintained for treatment duration. We predict that 1. When delivered by trained addiction counselors, MIO and PE can be discriminated; 2. MIO-assigned mothers will demonstrate greater improvement in reflective functioning and abstinence from substance use and their children will show greater improvement in attachment security at post-treatment and follow up; 3. MIO will confer greater advantage than PE for mothers with high addiction severity; and 4. Higher treatment fidelity will mediate better treatment outcomes and improvements in RF will mediate improvement in abstinence and child attachment security.